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Étude fonctionnelle et structurale de certains domaines des spectrines érythroïdes et non érythroïdes : site de tétramérisation et domaine SH3

Abstract : Spectrins are actin binding proteins that constitute the main components of membrane skeletons, the protein network located under the plasma membrane. Erythroid or non erythroid (in this case, they are called fodrins), spectrins play an important structural function in the membrane as demonstrated in the red blood cell. Spectrins are composed of two long α and β chains, associated in tetramers (αβ)2, forming the long flexible filaments of the network. Both chains are composed of repeating units which are folded in a triple helical arrangement (A, B and C helices), except for segment α10 which corresponds to a Src Homology 3 domain (SH3). The head-to-head interaction between dimers implies the N-terminal end of α chain and the C-terminal end of β chain. A model was proposed for the tetramerization site of spectrin : the two A and B helices of the last repeat of α chain interact with the C helix of the β chain in order to constitute a triple-helical structure similar to the repeats along the remainder of spectrin molecule. This model was first inferred from the relationship between the severity of the spectrin self-association defect and the location of the underlying mutations found in hereditary elliptocytosis (HE). Using recombinant peptides we defined the region, on both chains, which was sufficient and necessary to generate a fully functional tetramerization site. Producing peptides carrying a βHE mutation, we reproduced the tetramerization defect as observed in red blood cells of patients.
Finally, the presence of an SH3 domain probably gives to spectrins new functions which are different from the stability of the membrane. After contesting the existence of interaction between the fodrin SH3 domain and the α subunit of epithelial sodium channel sensitive to amiloride, we searched for partners of this domain, by screening a rat kidney library with the yeast two-hybrid system. We identified severals proteins implicated in the actin polymerization asoociated with motility or cell differenciation, suggesting that SH3 domain could play a part in this process.
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Submitted on : Tuesday, June 3, 2008 - 5:32:23 PM
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Gaël Nicolas. Étude fonctionnelle et structurale de certains domaines des spectrines érythroïdes et non érythroïdes : site de tétramérisation et domaine SH3. Sciences du Vivant [q-bio]. Université Paris-Diderot - Paris VII, 1999. Français. ⟨tel-00284819⟩

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